Molds with high glass fiber content made from quenched and tempered S136 steel will develop flash after producing just over 100,000 parts.
This is a situation many netizens have reported to me. Today, another netizen reached out—he’s injection molding PPS compound reinforced with 40% glass fiber. He’s currently using S136 mold steel, quenched and tempered to 50 HRC, but flash begins to appear after just over 100,000 parts. He learned a lot from my videos and ultimately decided to switch to 8503 mold steel, which resists material sticking.
Using S136 mold steel for injection molding of PPS with 40% glass fiber reinforcement is a material selection error, whereas switching to the non-stick 8503 mold steel is the correct approach. Since the PPS with 40% glass fiber reinforcement contains a high proportion of glass fiber, it causes severe erosion of the mold; therefore, the mold steel must possess both high hardness and non-stick properties.
S136 is a stainless steel with a carbon content of 0.38% and a hardness of only 50 HRC. Due to its low hardness and insufficient wear resistance, it cannot withstand the erosion caused by the PPS compound reinforced with 40% glass fiber. The mold will be worn away, resulting in flash on the products. The fact that flash began to appear after he had injection-molded over 100,000 products further corroborates this point. S136 is not suitable for use with a compound containing 40% glass fiber,
whereas 8503 mold steel has a hardness ranging from 55 to 61 HRC and twice the toughness of DC53. Compared to DC53, its performance is doubled without a corresponding increase in price, and it offers the added benefit of being non-stick. This non-stick property, combined with its high hardness, provides a fundamental and effective solution to the problem of molds being eroded by high-glass-fiber-content compounds, which leads to flash on the products.
Mr. Yu from Zhejiang says that for molds used with nylon reinforced with glass fiber, 8503 mold steel works exceptionally well—it can run continuously without developing flash. Additionally, Mr. Wang notes that for a 30% glass-fiber-reinforced nylon compound, 8503 mold steel can easily achieve a service life of 1 million cycles.
One user reported that when using S136 steel with a PPS + 40% GF compound, the mold wore out after producing just over 100,000 parts, resulting in flash on the products. This was due to incorrect material selection; you should have used 8503 mold steel, which resists material adhesion.
If you’re currently using S136, H13, SKD61, 2344, 8407—all medium-carbon steels with a carbon content of 0.38%—and harden them to 50 HRC, the parting lines will wear out quickly, products will develop flash, and the cavity surfaces will develop scratches. You won’t be able to solve these issues, so you should try the non-stick 8503 mold steel.
I’m Wu Dejian, the “King of Mold Steel,” from Dongguan Yuhui Mold Steel. Yuhui Mold Steel is used by three Fortune 500 companies, and Kyocera has been sourcing from us for seven consecutive years. If you’re unsure about which mold steel to choose, or if the mold steel you’re currently using results in short mold life and you don’t know which grade to switch to, come talk to me. I’ve helped over 4,000 companies solve complex challenges related to mold material selection, manufacturing, and usage. I’m confident that when it comes to selecting and applying mold steel, I can serve as your chief advisor and help you avoid costly trial-and-error.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.